1. Technical Field
The present invention relates to a liquid jet apparatus adapted to form predetermined characters and images by emitting microscopic droplets of liquids from a plurality of nozzles to form the microscopic particles (dots) thereof on a medium.
2. Related Art
An inkjet printer as one of liquid jet printing apparatuses using a liquid jet apparatus, which can generally provide low-price and high quality color prints with ease, has widely been spreading not only to offices but also to general users along with widespread of personal computers and digital cameras.
In the liquid jet printing apparatuses using the liquid jet apparatus, finer tone is required. The tone denotes a state of density of each color included in a pixel expressed by a liquid dot, the size of the dot corresponding to the color depth of a pixel is called a tone grade, and the number of tone grades which can be expressed by the dot is called a tone number. The fine tone denotes that the tone number is large. In order for changing the tone grade, it is required to modify a drive signal to an actuator provided to a liquid jet head. In the case in which a piezoelectric element is used as the actuator, since an amount of displacement (distortion) of the piezoelectric element (a diaphragm, to be precise) becomes large when a voltage value applied to the piezoelectric element becomes large, the tone grade of the liquid dot can be changed using this phenomenon.
Therefore, in JP-A-5-77456, it is arranged that a plurality of drive pulses power-amplified by an analog power amplifier and having different voltage wave heights are combined and joined to generate the drive signal, the drive signal is output from a control device commonly to the actuators of the nozzles of the same color provided to the liquid jet head, a drive pulse corresponding to the tone grade of the liquid dot to be formed is selected from the drive signal for each nozzle, and the selected drive pulses are supplied to the corresponding actuators to emit a jet of the liquid, thereby achieving the required tone grade of the dot. On the other hand, the analog power amplifier has large circuit loss, and needs some measures against heat generation or the like. Therefore, in JP-A-11-204850, the measures against heat generation can be eliminated by using a digital power amplifier with small circuit loss to amplify the drive signal.
However, in such a case as to perform printing with a line head-type printing apparatus, since it is required to drive a number of actuators with a common drive signal, the current value of the drive signal becomes larger. In the case of interposing an electric wire or a flexible flat cable (FFC) on an output terminal of the drive signal to the liquid jet head, if the current value of the drive signal is larger, the loss and the heat generation become larger, and therefore, it is required to use those having a conductor with a larger cross-sectional area, which not only incurs growth in size of the apparatus but also causes a problem of electromagnetic noise generation. Further, in the case in which the length of the electric wire or the FFC for outputting the drive signal to the liquid jet apparatus is larger, there is caused a problem that waveform distortion of the drive signal is generated due to the parasitic inductance or the like, thus the liquid jet characteristic is varied.